As the autonomous building block of the body, cells are known to have abilities to sense the local ambient environment and respond to external chemical and physical cues. Cells are also known to secret cytokines and hormones that are critical for homeostasis and useful for therapeutic purposes. Efforts have been made to employ these cellular functions for diagnosis and treatment by injecting specialized cells or implanting bioengineered cells in biological tissue, for example in patients. To make use of the cellular functions of so implanted specialized cells, it is often necessary to establish communication with these cells from a distance to be able to send regulatory control signals to the specialized cells or to receive signals, from these cells, that represent the cells' sensory response to the ambient.
Light offers an attractive means of communication with the cells in the biological system. Despite the great promise of light-mediated, cell-based sensing and therapy, there remain challenges that currently available phototherapeutic modalities have not overcome. Such challenges include high optical loss in the biological tissue due to scattering and absorption, a need to dispose the specialized cells in close proximity of the targeted biological tissue, low spatial density with which these specialized cells can be juxtaposed with the biological tissue (which leads to the need to illuminate these cells and collect cells' sensory signals at low intensity levels), and a need to removably bring the source of light (for example, an optical fiber) irradiating the specialized cells in contact with or inside the tissue itself, to name just a few.
There remains, therefore, a need in a methodology that facilitates light delivery into cells implanted in a biological tissue at at least dermatological depths or deeper (in order to, for example, photo-activate light-matter interaction processes in the tissue), that overcomes the abovementioned challenges, and that does not cause trauma associated with a post-irradiation removal of the light-delivery system from the tissue.